The splanchnic nerves are the nerves that supply signals and information to and from the visceral organs and blood vessels. They are typically divided into three different categories based on their location in the body. Cardiopulmonary nerves control the organs of the thoracic cavity, carrying messages from the central nervous system to the heart and the lungs. Lumbar nerves are responsible for the signals sent and received by the abdominal digestive organs. Pelvic splanchnic nerves transmit the signals necessary for urination, bowel movements and sexual functions.
Most of the sympathetic nerves of the body are splanchnic. These nerves are carriers of unconscious signals the central nervous system (CNS) sends to regulate the many functions of the body. This includes the ability to form tears, salivate, and digest food. The afferent nerves are sensory nerves that carry the messages to the brain about the sensations the body is experiencing. Efferent nerves are motor nerves that communicate the need for action on the part of the organs or muscles to maintain the efficiency of the human body.
The brain commands the heart and lungs to operate at a peak performance level through the cardiopulmonary nerves. The thoracic cavity is lined with these nerves, and is coordinated with the needs of the rest of the body through the central nervous system. Sensory nerves can detect the oxygen levels of the blood and relay the message to the heart and lungs to adjust accordingly.
Lumbar splanchnic nerves are necessary for the digestion of food through the stomach and into the intestines. These nerves carry signals to the brain to increase or decrease the amount of gastric juices secreted by the stomach at the start of the digestive process. They also control the peristaltic movement of the intestines that encourages food to move through the digestive tract.
Pelvic splanchnic nerves also conclude the digestive process. These nerves signal the bladder to release urine when it has reached capacity. The nerves also detect when a bowel movement has formed, and in turn, signal the nerves in the rectum to relax to allow the passage of the fecal matter. Blood flow to the male genitals necessary for arousal and the completion of the sex act is also regulated by pelvic nerves. In females, these nerves indicate the need for vaginal lubrication and transmits the sensory information necessary for the reproductive organs to function.